It has been clear for several decades that high total cholesterol, high triglycerides, low high-density lipoprotein cholesterol, normal to elevated low-density lipoprotein cholesterol, or small low-density lipoprotein particles are related to a variety of diseases, conditions and disorders.
The evidence linking elevated serum cholesterol to coronary heart disease is overwhelming. (Badimon et al., Circulation, 86 Suppl. III, 1992, 86-94). Circulating cholesterol is carried by plasma lipoproteins, which are complex particles of lipid and protein that transport lipids in the blood. Low density lipoprotein (LDL) and high density lipoprotein (HDL) are the major cholesterol-carrier proteins. Id. LDL is believed to be responsible for the delivery of cholesterol from the liver, where it is synthesized or obtained from dietary sources, to extrahepatic tissues in the body. The term “reverse cholesterol transport” describes the transport of cholesterol from extrahepatic tissues to the liver, where it is catabolized and eliminated. It is believed that plasma HDL particles play a major role in the reverse transport process, acting as scavengers of tissue cholesterol. Id. HDL is also responsible for the removal non-cholesterol lipid, oxidized cholesterol and other oxidized products from the bloodstream.
Atherosclerosis, for example, is a slowly progressive disease characterized by the accumulation of cholesterol within the arterial wall. Compelling evidence supports the belief that lipids deposited in atherosclerotic lesions are derived primarily from plasma apolipoprotein B (apo B)-containing lipoproteins, which include chylomicrons, CLDL, IDL and LDL. See Badimon et al., 1992, Circulation 86:(Suppl. III) 86-94. The apo B-containing lipoprotein, and in particular LDL, has popularly become known as the “bad” cholesterol. In contrast, HDL serum levels correlate inversely with coronary heart disease. Indeed, high serum levels of HDL is regarded as a negative risk factor. It is hypothesized that a high level of plasma HDL is not only protective against coronary artery disease, but may actually induce regression of atherosclerotic plaque. See Dansky and Fisher, 1999, Circulation 100: 1762-3. Thus, HDL has popularly become known as the “good” cholesterol.
Further, dyslipidemia is caused by various factors including, but not limited to, high total cholesterol, high triglycerides, low high-density lipoprotein cholesterol, normal to elevated low-density lipoprotein cholesterol, or small low-density lipoprotein particles.
Thus, there is a continued need to find new therapeutic agents to treat lipoprotein abnormalities. Accordingly, there is a great need to develop compounds and pharmaceutical compositions that will raise HDL levels, lower LDL levels, and/or lower triglyceride levels in a subject.